Narrative:

While in cruise flight at FL300; a loud 'thud' was heard and the #1 engine rolled-back to approximately 50% N1. The engine 1; N1 vibration was excessive. The speed began to slow and; with the concurrence of the first officer; I brought the #1 thrust lever back to idle and pushed the #2 thrust lever to the mct [maximum continuous thrust] detent. I advised ATC we had a problem with one of our engines and needed a lower altitude right away. The flight attendants called immediately and I told them we were aware of the problem; 'it's ok;' and I would get back to them and make a PA as soon as I could. We were eventually cleared to maintain FL200. I asked the first officer to continue to fly and I would work on the problem. As he descended; I reviewed the QRH and ECAM supplemental books for high engine vibration. I started the APU. I asked ATC for a holding clearance while we trouble-shot our problem. I told them we would more than likely be diverting to ZZZ but would get back to them. I then called the flight attendants back; explained the problem; told them we would probably be landing in ZZZ in 20 or so minutes; to begin to prepare for a landing and I would get back to them before we began the approach to check on them. I then made a PA and tried to set the passengers at ease. We advised maintenance control and dispatch. I advised that we were overhead ZZZ and didn't feel it was prudent to go anywhere else. They agreed. So the mutual decision was to land in ZZZ. I asked the dispatcher to coordinate with the ZZZ station and advise them we would be landing in about 20 minutes. I got back to ATC and made sure we officially declared an emergency; and gave them all of their required information. The first officer and I then began to run through all of the checklist items that needed to be done while we continued to hold at 20;000'. We changed our destination; in the FMS; loaded the approach; briefed the approach; reviewed all of the landing distance requirements; overweight landing checklist; we reviewed the engine shutdown and associated checklist for items that applied to our situation. We did not shut the engine down; so this checklist did not fully apply. We discussed the pros and cons of shutting the engine down. We tested the thrust capability of the engine. We were able to get 50% N1 out of the engine. We decided that a go-around at our heavy weight would be a challenge; so a decision was made to keep the thrust at idle; taking advantage of the extra generator; the APU bleed for running the packs which would allow for additional thrust for the go-around; and the piece of mind that we could get 50% out of the engine if we needed it. The N1 vibration remained at 9.9 at idle thrust. It actually went down to 6.7 at 50% N1; but we returned it to idle for the remainder of the flight. After we ran all of the checklist; I asked the first officer if there was anything else we hadn't thought of and did he feel comfortable flying the approach. He said he couldn't think of anything else and yes; he was fine flying the approach. I then called the flight attendants to see if they were ready. They were. I told them to expect a normal landing; no need to brace. I then made another PA to the passengers; telling them what to expect. We were switched to ZZZ approach control and vectored for the ILS. The approach and landing were normal. We touched down at 177;500 pounds with a 100 FPM sink rate. We taxied to the gate without assistance. After the passengers deplaned; we went out to inspect the engine with a mechanic. The front fan looked normal. We then looked in the tail-pipe and found the last two sections of turbine rotors were almost completely gone so that's why we had excessive N1 vibration with normal looking fan blades.

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Original NASA ASRS Text

Title: An A321 Flight Crew suffered a near catastrophic engine failure. They diverted to land but did not shut down the engine.

Narrative: While in cruise flight at FL300; a loud 'thud' was heard and the #1 engine rolled-back to approximately 50% N1. The Engine 1; N1 Vibration was excessive. The speed began to slow and; with the concurrence of the First Officer; I brought the #1 thrust lever back to idle and pushed the #2 thrust lever to the MCT [Maximum Continuous Thrust] detent. I advised ATC we had a problem with one of our engines and needed a lower altitude right away. The Flight Attendants called immediately and I told them we were aware of the problem; 'it's OK;' and I would get back to them and make a PA as soon as I could. We were eventually cleared to maintain FL200. I asked the First Officer to continue to fly and I would work on the problem. As he descended; I reviewed the QRH and ECAM Supplemental Books for High Engine Vibration. I started the APU. I asked ATC for a holding clearance while we trouble-shot our problem. I told them we would more than likely be diverting to ZZZ but would get back to them. I then called the Flight Attendants back; explained the problem; told them we would probably be landing in ZZZ in 20 or so minutes; to begin to prepare for a landing and I would get back to them before we began the approach to check on them. I then made a PA and tried to set the passengers at ease. We advised Maintenance Control and Dispatch. I advised that we were overhead ZZZ and didn't feel it was prudent to go anywhere else. They agreed. So the mutual decision was to land in ZZZ. I asked the Dispatcher to coordinate with the ZZZ Station and advise them we would be landing in about 20 minutes. I got back to ATC and made sure we officially declared an Emergency; and gave them all of their required information. The First Officer and I then began to run through all of the checklist items that needed to be done while we continued to hold at 20;000'. We changed our destination; in the FMS; loaded the approach; briefed the approach; reviewed all of the landing distance requirements; overweight landing checklist; we reviewed the engine shutdown and associated checklist for items that applied to our situation. We did not shut the engine down; so this checklist did not fully apply. We discussed the pros and cons of shutting the engine down. We tested the thrust capability of the engine. We were able to get 50% N1 out of the engine. We decided that a go-around at our heavy weight would be a challenge; so a decision was made to keep the thrust at idle; taking advantage of the extra generator; the APU bleed for running the packs which would allow for additional thrust for the go-around; and the piece of mind that we could get 50% out of the engine if we needed it. The N1 Vibration remained at 9.9 at idle thrust. It actually went down to 6.7 at 50% N1; but we returned it to idle for the remainder of the flight. After we ran all of the checklist; I asked the First Officer if there was anything else we hadn't thought of and did he feel comfortable flying the approach. He said he couldn't think of anything else and yes; he was fine flying the approach. I then called the Flight Attendants to see if they were ready. They were. I told them to expect a normal landing; no need to brace. I then made another PA to the passengers; telling them what to expect. We were switched to ZZZ Approach Control and vectored for the ILS. The approach and landing were normal. We touched down at 177;500 LBS with a 100 FPM sink rate. We taxied to the gate without assistance. After the passengers deplaned; we went out to inspect the engine with a Mechanic. The front Fan looked normal. We then looked in the tail-pipe and found the last two sections of turbine rotors were almost completely gone so that's why we had excessive N1 vibration with normal looking fan blades.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.